Thermostat responsive to inputs from external devices

ABSTRACT

A thermostat is provided that receives one or more inputs from at least one heating system of a climate control system, and initiates an appropriate action in response to the input. The thermostat can turn off a heat pump providing substandard heat and responsively turn on a fuel-fired auxiliary furnace. The thermostat may discontinue further operation of the auxiliary furnace upon receiving an operating error signal associated with the auxiliary furnace, and responsively turn on the heat pump to provide for continued heating. The thermostat may also discontinue operation of the fuel-fired furnace and turn on a circulating fan in response to an input signal indicating a furnace high-temperature or a carbon monoxide presence.

FIELD OF THE INVENTION

The present invention relates to thermostats, and in particular, tothermostats used for controlling climate control systems that include afuel-fired heating system and or a heat pump system.

BACKGROUND OF THE INVENTION

Thermostats are typically used to control climate control systems tomaintain the temperature of the space conditioned by the climate controlsystem. A conventional thermostat compares the sensed temperature of thespace with a set point temperature and activates the climate controlsystem to heat or cool the space to the desired set point temperature.Some heating systems may comprise a fuel-fired heating system, whileothers comprise a heat pump and an auxiliary heat system. In the case ofa single heating system, the conventional thermostat controls the systemby turning on the fuel-fired furnace when there is a demand for heating,and turning on a higher second stage of heating (if present) when thereis an increased demand for heating. In the case of a dual heat system,the conventional thermostat controls both systems by turning on the heatpump when there is a demand for heating, and turning on the auxiliaryheat system when the heat pump is not adequately providing heating dueto low outside temperatures. Such dual heat systems using an auxiliaryor supplemental heat system may comprise a fuel-fired furnace. However,present conventional thermostats cannot identify problems with a heatpump or a fuel-fired furnace. In fact, an operating problem in eithersystem may result in an inability of the climate control system toachieve the set point temperature, and the thermostat would onlyexacerbate the problem by continuing to request operation of theproblematic system.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a preferredembodiment of a digital thermostat is provided that receives one or moreinputs from at least one heating system of a climate control system, andinitiates an appropriate action in response to the input. The digitalthermostat for controlling the operation of a climate control systemhaving at least a heat pump system and an auxiliary heating system,comprising a display means for visually displaying operating errorinformation to a user of the thermostat, a temperature sensor forsensing the outside ambient temperature, and a processor having an inputmeans for receiving at least one communication signal from either theheat pump or auxiliary heating system indicating whether the heat pumpor auxiliary heating system is not operating. The processor of thedigital thermostat responds to the non-operating communication signal byinitiating the deactivation of the non-operating system and theactivation of the other operable system.

In another aspect of the present invention, some embodiments of athermostat are provided that are capable of receiving a communicationsignal from an auxiliary heating system controller indicating theauxiliary heating system is not operating, and responsively initiatingthe activation of the heat pump system even if the outside ambienttemperature is below the predetermined temperature value. Likewise, someembodiments of the present invention provide a thermostat capable ofreceiving a communication signal from a heat pump system indicating theheat pump system is not operating, and responsively initiating theactivation of the auxiliary heating system. The thermostat is alsocapable of sensing a predetermined decrease in indoor temperature whileone of either the heat pump system or the auxiliary heating system isoperating, and responsively deactivating the operating system andactivating the other system.

In yet another aspect of the present invention, the preferred embodimentof a digital thermostat comprising an LCD display and input means forreceiving at least one input signal from at least one apparatus of aclimate control system is capable of initiating an appropriate action inresponse to receiving an input signal to provide for improved controlthe climate control system. The thermostat may discontinue a call forsecond stage heating in response to receiving an input of a lock-out ofsecond stage furnace operation. The thermostat may also discontinueoperation of the fuel-fired furnace and turn on a circulating fan inresponse to receiving an input signal indicating a furnacehigh-temperature condition or a carbon monoxide presence. The thermostatis configured to display the information associated with the inputsignal on the display of the thermostat, and to ascertain whether acorrective action should be taken that appropriately addresses the inputsignal.

BRIEF DESCRIPTION OF THE DRAWINGS

The sole FIGURE is an illustration of a climate control systemincorporating a thermostat according to the principles of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

A thermostat for controlling a climate control system in whichembodiments of the present invention can be implemented is indicatedgenerally as 100 in the sole FIGURE. The climate control system includesat least one heating system, and may be single-stage or multi-stagefuel-fired heating system or a combined heat pump and auxiliaryfuel-fired heating furnace 110. Typically, a heat pump comprises anoutside unit 124 having a controller 130 and a compressor forcompressing a refrigerant that transfers heat to an inside A-coil heatexchanger 122. The connections may comprise one or more wires betweenthe thermostat 100 and the heat pump control 120 and fuel-fired furnacecontrol 112, or the connections to the various systems could comprise aRS 485 or a RS-232 communication means, or RF communication or otherwireless communication means. In one preferred embodiment, thethermostat 100 comprises an input connection means for RS 485communication to a processor of the thermostat 100, where the inputconnection may be connected to a plurality of external devices. Theprocessor of the present invention is generally a microprocessor, and ispreferably a 32 Kb memory microprocessor S3C8249Xzz-OWR9 manufactured bySamsung which comprises an RS 485 input port pin.

The communication means in the preferred embodiment comprises a two-wirepeer-to-peer network, such as a RS-485 peer-to-peer Local Area Network,but may alternatively comprise any other comparable network suitablesuch as a RS-232 network for use in a two-way communication arrangement.The RS-485 network is a two-wire, multi-drop network that allowsmultiple units to share the same two wires in sending and receivinginformation. The two-wire network connects to the processor of thethermostat and to each controller in the HVAC system, such as the heatpump controller or an auxiliary heating system controller. Thethermostat and controllers are always enabled in the receiver mode,monitoring the network for information. Only one transmitter cancommunicate or occupy the network at a time, so each individualcontroller is configured to transmit at a fixed time period after thelast transmission, where each controller has a fixed time period that isunique to that controller. Thus, after one controller completes itstransmission, another controller will wait for the prescribed timeperiod before transmitting its information. In this manner, collisionsof data transmission from different controllers may be avoided. Thetransmissions may also include leader information at the beginning ofeach transmission, which identifies the controller that the transmissionpertains to.

In response to an error input signal from the heat pump control 120 orfurnace control 112 or other device external to the thermostat, thethermostat 100 can respond in one or more ways, including (1) displayinginformation associated with the input signal on a display of thethermostat 100, (2) discontinuing further second stage operation of thefurnace, (3) discontinuing the call for heating and turning on thecirculation blower fan, (4) discontinuing all further operation of thefurnace, (5) discontinuing operation of the heat pump, if applicable,and initiating operation of the fuel-fired furnace, and (6)discontinuing operation of the fuel-fired furnace and initiatingoperation of the heat pump only, if applicable. In response to receivingan input signal from a fuel-fired furnace control 112 indicating a hightemperature condition in the furnace heat exchanger, the processor ofthe thermostat 100 may discontinue heating operation of the fuel-firedfurnace and turn on a circulation blower fan of the furnace until thehigh temperature condition ends. In response to receiving an inputsignal from a fuel-fired furnace control 112 of an error from acirculation air pressure switch 116, the thermostat 100 may indicate onthe display of the thermostat a request to check or replace the airfilter. In response to an input signal from a fuel-fired furnace control112 indicating a lock-out of second stage heating, the processor of thethermostat 100 may discontinue further calls for second stage heatingand only call for normal heating. In response to an input signal from afurnace control 112 indicating the furnace is locked-out due to repeatedignition failure or flame sense 114 failure, the thermostat 100 maydiscontinue further calls for operation of the furnace and, ifavailable, call for operation of a heat pump. Likewise, in response toan input signal from a heat pump control 120 indicating the heat pumpcompressor is inoperable due to locked-rotor or other failure, thethermostat 100 may discontinue further calls for operation of the heatpump and, if available, call for operation of an auxiliary fuel-firedfurnace.

In the preferred embodiment of a thermostat incorporating the principlesof the present invention, the thermostat is intended for use with one ormore heating systems, and can receive one or more inputs from at leastone heating system and initiate an appropriate action corresponding tothe input. Where the thermostat is used in a dual heat system, thethermostat 100 can turn off a heat pump that is providing substandardheat as a result of near freezing outside temperatures and call foroperation of an auxiliary or supplemental heating system. The auxiliaryheating system may be of the fuel-fired furnace type having a furnacecontrol 112. If after the thermostat 100 calls for operation of theauxiliary fuel-fired furnace the thermostat 100 receives an input signalindicating the fuel-fired furnace is locked-out or not operating, thethermostat may discontinue the call for operation of the auxiliaryfuel-fired furnace and call for heat pump operation only to maintain asupply of heating for the space. Where the auxiliary fuel-fired furnaceis not capable of providing an operating fault input to the thermostat,the thermostat 100 is configured to sense a decrease in temperature ofthe space during operation of the fuel-fired furnace. If after thethermostat 100 calls for operation of the auxiliary fuel-fired furnacethe temperature of the space decreases more than a predetermined amount,the thermostat 100 may discontinue the call for operation of theauxiliary fuel-fired furnace and call for heat pump operation only.

In the preferred embodiment, the thermostat 100 may also be connected toother devices external to the thermostat associated with the climatecontrol system, including a furnace flue pressure sensor 118, a carbonmonoxide sensor 132 and a smoke detector 134. The thermostat 100 mayreceive an input signal from a flue pressure sensor indicating the flueof a fuel-fired furnace is blocked, and respond by discontinuing furtheroperation of the fuel-fired furnace to prevent combustion air in theflue from accumulating in the space. The thermostat 100 may similarlyreceive an input signal from a smoke detector indicating the presence ofsmoke in the space, and respond by discontinuing further operation ofthe fuel-fired furnace. The thermostat 100 may also receive an inputsignal from a carbon monoxide sensor indicating the presence of carbonmonoxide, and respond by discontinuing further operation of thefuel-fired furnace and turning on the circulation blower fan. In a dualheating climate control system, the thermostat 100 may also call foroperation of a heat pump if available after discontinuing operation ofthe fuel-fired furnace. It should be appreciated that in the preferredembodiment the thermostat may be configured to provide an appropriateresponse to any number of input signals from one or more apparatus in aclimate control system.

The thermostat 100 may be configured to include an RS 485 or an RS 232connection for receiving input signals from a plurality of externaldevices, and a monitoring means for analyzing and identifying the sourceof the input signal. The monitoring means enables the processor of thethermostat 100 to determine which system or apparatus the input signalcorresponds to, for initiating an appropriate action in response to theinformation received through the RS 485 connection to the thermostat100. Thus, the thermostat 100 implementing the present invention canrespond to informational and error input signals, in various wayscomprising the display of information associated with the input signalon a display of the thermostat, and the control of one or more heatingapparatus in a climate control system.

It should be noted that the thermostat display may be used to display adescription of the information received in the input signal and the timeof the signal, for the purpose of trouble-shooting the climate controlsystem. The information may also be communicated through other displaymeans such as an LED that is flashed on and off to provide an opticalsignal that may be read by the user of the thermostat or by a flashingLight Emmitting Diode (LED) used by a technician. Likewise, theinventive thermostat may be configured to be used with other apparatusnot included in the preceding embodiment, such as an air conditioner ofa climate control system.

Additional design considerations, readily apparent to one of ordinaryskill in the art, such as the modification of the thermostat to provideerror or fault information on the LCD display may also improve theuser's ability to correct a problem in the climate control system. Itshould be apparent to those skilled in the art that variousmodifications such as the above may be made without departing from thespirit and scope of the invention. More particularly, the apparatus maybe adapted to any apparatus for controlling a climate control system.Accordingly, it is not intended that the invention be limited by theparticular form illustrated and described above, but by the appendedclaims.

1. A digital thermostat for controlling the operation of a climatecontrol system having at least a heat pump system and an auxiliaryheating system, comprising: a display means for visually displayingoperating error information to a user of the thermostat; a temperaturesensor for sensing the outside ambient temperature; a processor beingconfigured to deactivate the heat pump system in response to thetemperature sensor sensing an outside ambient temperature below apredetermined temperature value, and configured to responsively activatethe auxiliary heating system, said processor having an input means forreceiving at least one communication signal from either the heat pump orauxiliary heating system indicating whether the heat pump or auxiliaryheating system is not operating, wherein the processor responds to thenon-operating communication signal by initiating the deactivation of thenon-operating system and the activation of the other operable system,and where the communication signal is a signal from an auxiliary heatingsystem controller indicating the auxiliary heating system is notoperating, the processor responsively initiates the activation of theheat pump system even if the outside ambient temperature is below thepredetermined temperature value.
 2. The digital thermostat of claim 1,where if upon activating the auxiliary heating system the digitalthermostat senses a predetermined decrease in indoor temperature whilethe auxiliary heating system is operating, the processor deactivates theauxiliary heating system and activates the heat pump system even if theoutside ambient temperature is below the predetermined temperaturevalue.
 3. The digital thermostat of claim 1, wherein the communicationsignal is a signal communicated by a heat pump controller indicating theheat pump system is not operating.
 4. The digital thermostat of claim 3,wherein the processor responds to the non-operating heat pumpcommunication signal by controlling the activation of the auxiliaryheating system.
 5. The digital thermostat of claim 1, where if uponactivating the heat pump system the digital thermostat senses apredetermined decrease in indoor temperature while the heat pump systemis operating, the processor deactivates the heat pump system andactivates the auxiliary heating system.
 6. A digital thermostat forcontrolling the operation of a climate control system having at least aheat pump system and an auxiliary heating system, comprising: a displaymeans for visually displaying operating error information to a user ofthe thermostat; a temperature sensor for sensing the outside ambienttemperature; a processor being configured to deactivate the heat pumpsystem in response to the temperature sensor sensing an outside ambienttemperature below a predetermined temperature value, and configured toresponsively activate the auxiliary heating system said processor havingan input means for receiving at least one communication signal fromeither the heat pump or auxiliary heating system indicating whether theheat pump or auxiliary heating system is not operating, where inresponse to receiving a communication signal indicating the auxiliaryheating system is not operating and subsequently sensing an outsideambient temperature below the predetermined temperature value, thethermostat processor responsively continues to continues to operate theheat pump system during a call for heating.
 7. A digital thermostat forcontrolling the operation of a climate control system having at least afuel-fired furnace, comprising: a display means for visually displayinginformation to the user of the digital thermostat; and a processorhaving an input means for receiving at least one input signal from afurnace controller communicating operating error code informationrelating to the furnace, wherein the processor responsively communicatesto the display means the information to be displayed to the user of thethermostat, and where in response to a first error code signal from thefurnace controller indicating an increase in circulation air pressurethe processor signals the display means to display a request to changethe air filter.
 8. The digital thermostat of claim 7, where in respondsto a predetermined error code the processor controls the activation ordeactivation of one or more devices within the climate control system.9. The digital thermostat of claim 7, where in response to a seconderror code signal from the furnace controller indicating a highheat-exchanger temperature the processor discontinues the furnaceoperation and activates the circulator blower fan.
 10. The digitalthermostat of claim 7, where in response to a third error code signalfrom the furnace controller indicating a furnace lock out of secondstage operation the processor discontinues the thermostat's call forsecond stage furnace operation and subsequently calls for first stagefurnace operation only.
 11. The digital thermostat of claim 7, where inresponse to a fourth error code signal from the furnace controllerindicating a flame sense failure the processor discontinues heatingoperation of the fuel-fired furnace.
 12. The digital thermostat of claim7, further comprising a connector for connecting the processor to asmoke detector.
 13. The digital thermostat of claim 12, wherein theprocessor responds to a signal from the smoke detector by discontinuingthe thermostat's call for furnace operation and signaling the displaymeans to display a smoke detector alarm to the thermostat user.
 14. Animproved digital thermostat for controlling the operation of a climatecontrol system comprising at least a fuel-fired furnace, the improvementcomprising: a display means for visually displaying error signalinformation from a climate control system to the user of the digitalthermostat; a processor having an input means for receiving at least oneinput signal from a furnace controller indicating an operating errorsignal from the controller wherein the operating information signal fromthe furnace controller comprises at least one error code signalcommunicated by the furnace controller; and wherein the processorresponds to a predetermined error code by controlling the activation ordeactivation of one or more devices within the climate control system,wherein the processor responds to a first error code signal from thefurnace controller indicating a change in circulation air pressure bysignaling the display means to display a request to change the airfilter.
 15. The improved thermostat of claim 14, wherein the processorresponds to a second error code signal from the furnace controllerindicating a high heat-exchanger temperature by discontinuing thethermostat's call for furnace operation and activating the circulatorblower fan.
 16. The improved thermostat of claim 14, wherein theprocessor responds to a third error code signal from the furnacecontroller indicating a furnace lock out of second stage operation bydiscontinuing the thermostat's call for second stage furnace operationand subsequently calling for first stage furnace operation only.